Transcript Document

Swine flu
Etiology
influenza virus is an orthomyxovirus.
This type of virus is divided into three groups;
type A, type B or type C.
Type A viruses are further divided into
subtypes based on their hemaglutinin (H)
and neuraminidases (N).
Influenza virus structure
… A ssRNA enveloped virus
with 8 pieces (genes)
of RNA
… With 2 surface glycoprotein
Spikes – H and N
… And hemispheric clades of 15 H genes, 9 N genes
E.g. “H5N1” Bird flu ….
U.S. orders $200 million in H5N1 bird flu
vaccine
Influenza changes
1. by antigenic drift of HA and NA,
2. by cleavage of the HA,
3. by HA changing to bind to different
receptors
and, further by “shift” through
Genetic Reassortment
Swine Flu and Virus
Swine Influenza (swine flu) is a respiratory disease of
pigs caused by type A influenza virus that regularly
causes outbreaks of influenza in pigs. Swine flu
viruses cause high levels of illness and low death
rates in pigs. Swine influenza viruses may circulate
among swine throughout the year, but most
outbreaks occur during the late fall and winter
months similar to outbreaks in humans. The
classical swine flu virus (an influenza type A H1N1
virus) was first isolated from a pig in 1930.
Swine Flu differs from Human Flu
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At this time, there are four main
influenza type A virus subtypes
that have been isolated in pigs:
H1N1, H1N2, H3N2, and H3N1.
However, most of the recently
isolated influenza viruses from
pigs have been H1N1 viruses.
The H1N1 swine flu viruses are
antigenically very different from
human H1N1 viruses and,
therefore, vaccines for human
seasonal flu would not provide
protection from H1N1 swine flu
viruses
Why Pigs?
1-Ducks and pigs are raised by humans in
close proximity.
2-Pig cells have virus receptors (virus
binding capability) for both avian and
mammalian influenza strains
Influenza Reassortment
New
Strain
Domestic
Duck or Chicken
Mixed infection of a pig
New Reassortment
of Influenza virus
gene segments arises
in a pig
Many H5N1-infected chickens
Few H5N1-infected humans
No human-to-human transmission
Many H5N1-infected chickens
Reassort genes
Many H5N1-infected humans
Moderately efficient human-to-human
Elements of a pandemic: Many H5N1-infected humans
Good human-to-human transmission
Stable Species Jumps or
“Evolutionary Transmissions”
Stable Species Jumps or
“Evolutionary Transmissions”
MAP of H1 N1 Swine Flu
Summary
U.S.
Deaths
% pop
Global
deaths
% global
pop
1918
660,000
0.60
20-40 M
1.3-2.5
1957
70,000
0.04
1968
34,000
0.02
102,086
0.04
2.0 M
0.03
315,200
0.11
7.4 M
0.12
Year
Next: low
estimate
Next: high
estimate*
Transmission:
Swine flu is contagious and is spreading from human to
human. However, at this time, it is not known how easily
the virus spreads between people.
Swine flu is thought to be spread from person to person in
the same way seasonal influenza and other common
respiratory infections spread.
Being in close contact (eg. within a metre) with an infected
person while they are talking, coughing or sneezing puts
you at risk of becoming infected. Virus-containing droplets
can land on the surfaces of the mouth, nose and throat
of people close by. The virus may also be spread
through contact with infectious respiratory secretions on
the hands of an infected person or other objects and
surfaces.
How long can viruses live outside the
body?

We know that some viruses and bacteria can
live 2 hours or longer on surfaces like
cafeteria tables, doorknobs, and desks.
Frequent hand washing will help you reduce
the chance of getting contamination from
these common surfaces.
Infectious Period
People with swine influenza virus infection
should be considered potentially contagious
as long as they are symptomatic and possibly
for up to 7 days following illness onset.
Children, especially younger children, might
potentially be contagious for longer periods.
How Swine Flu presents in Humans

The symptoms of swine flu
in people are expected to
be similar to the symptoms
of regular human seasonal
influenza and include fever,
lethargy, lack of appetite
and coughing. Some people
with swine flu also have
reported runny nose, sore
throat, nausea, vomiting
and diarrhea
Seek emergency medical care.
IF - in Children
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In children emergency warning signs that need
urgent medical attention include:
Fast breathing or trouble breathing Bluish skin
color.Not drinking enough fluids
Not waking up or not interacting
Being so irritable that the child does not want to be
held
Flu-like symptoms improve but then return with fever
and worse cough
Fever with a rash
Diagnosis

To diagnose swine
influenza A infection, a
respiratory specimen
would generally need to
be collected within the
first 4 to 5 days of
illness (when an infected
person is most likely to
be shedding virus).
However, some persons,
especially children, may
shed virus for 10 days or
longer. Identification as a
swine flu influenza A
virus
No Vaccines to Humans
But available to PIGS

Vaccines are available to
be given to pigs to
prevent swine influenza.
There is no vaccine to
protect humans from
swine flu. The seasonal
influenza vaccine will
likely help provide partial
protection against swine
H3N2, but not swine
H1N1 viruses.
Drugs which are effective in Swine Flu
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There are four different
antiviral drugs that are
licensed for use in the
US for the treatment of
influenza: Amantidine,
rimantadine,
oseltamivir and
zanamivir. While most
swine influenza viruses
have been susceptible
to all four drugs
Thanks